Adsorbate Coverage Research Articles

Unexpected inhibition roles of methane nanobubbles on hydrate decomposition

Uncontrolled hydrate decomposition poses extraordinary risks, such as submarine landslides during hydrate exploitation, and gas leakage during hydrate storage/transportation. Previous studies suggested inhibitors can effectively prevent hydrate decomposition by adsorbing onto the hydrate surface. However, herein, we find inhibitors have very limited adsorption coverages on hydrate, which cannot fully explain their good performance. In this study, by combining experiments and molecular simulations, a new inhibition mechanism is proposed, in which nanobubbles act as the primary factor in inhibiting hydrate decomposition. Specifically, when PVP (a typical inhibitor) is added into the solution, its hydrophobic groups interact strongly with CH4, thereby increasing CH4 solubility and inducing the formation of CH4 nanobubbles. These nanobubbles are then encapsulated within the hydrate and inhibit hydrate decomposition by the following process: nanobubbles gradually become exposed to the aqueous phase during hydrate decomposition and release CH4 to the region near the nanobubble-hydrate interface. The high local CH4 concentrations near the nanobubble-hydrate interface would promote the formation of microstructures necessary for hydrate nucleation, thereby amplifying the driving force toward nucleation and consequently inhibiting hydrate decomposition. Our proposed “nanobubble inhibition mechanism” can provide a theoretical foundation for developing and applying inhibitors to prevent hydrate decomposition in various industrial applications.

Hydrogen adsorption on zinc-terminated ZnO(0001) surface at varying coverages and its effects on electronic and optical properties: a DFT+U study

Abstract Spin-polarized density functional theory implementing Hubbard corrections (DFT + U) were utilized to study H adsorption of different coverages on Zn-terminated ZnO(0001) surface. Changes in electronic and optical properties were observed upon H adsorption of varying coverages, namely with 0.25 monolayer (ML), 0.50 ML, 1 ML, and 2 ML coverage. In terms of surface structure, H atoms were found to adsorb on top of Zn forming Zn–H bond lengths ranging from 1.54–1.73 Å for certain coverages. On the other hand, O–H bond length values are 2.41 Å and 2.37 Å for 0.50 ML and 2 ML coverage respectively. Additionally, for 0.50 ML, the most stable configuration is when one H atom adsorbs on top of Zn and the other near the hollow site. At low coverage (0.25 ML and 0.50 ML), H prefers to interact with topmost layer Zn atoms resulting to shifts in the electronic bands relative to the pristine surface’s. In addition, at high coverage (1 ML and 2 ML), shifting of bands are observed and are mainly guided by Zn–H atom interaction for 1 ML and weak H–O atom interaction for 2 ML. The observed decrease in band gap as the coverage was increased from 1 ML to 2 ML is supported by the red shift in the absorption plot. However, for low H coverage adsorption, the optical plots deviate due to emergence of flat bands. Changes in electronic properties such as shifts in conduction band minimum and decrease in measured band gap occur as guided by the interaction of adsorbed H atoms with the surface atoms and are supported with obtained optical plots. These findings present the tunability of Zn-terminated ZnO(0001) polar surface properties depending on H coverage.

Understanding the Electrochemical Carbon Dioxide Reduction Reaction Mechanism of Lattice Tuning of Copper by Silver Single-Crystal Surface.

Intermolecular interactions and adsorbate coverage on a metal electrode's surface/interface play an important role in CO2 reduction reaction (CO2RR). Herein, the activity and selectivity of CO2RR on bimetallic electrode, where a full monoatomic Cu layer covers on Ag surface (CuML/Ag) are investigated by using density functional theory calculations. The surface geometric and electronic structure results indicate that there is high electrocatalytic activity for CO2RR on the CuML/Ag electrode. Specifically, the CuML/Ag surface can accelerate the H2O and CO2 adsorption and hydrogenation while lowering the reaction energy of the rate-determining step. The structure parameters of chemisorbed CO2 with and without H2O demonstrate that activated H2O not only promotes the C-O dissociation but also provides the protons required for CO2RR on the CuML/Ag electrode surface. Furthermore, the various reaction mechanism diagrams indicate that the CuML/Ag electrode has high selectivity for CO2RR, and the efficiency of products can be regulated by modulating the reaction's electric potential.

Computational insight into the selectivity of [formula omitted]-valerolactone hydrodeoxygenation over Rh(111) and Ru(0001)

The observed difference in the selectivity towards alkane, ketone, and alcohol hydrodeoxygenation products over Ru and Rh catalysts is explored using a combination of density functional theory and microkinetics. Using γ-valerolactone as a model compound, we investigate the reaction mechanism in order to identify selectivity determining species. The effect of the coadsorbed water molecule as well as the higher adsorbate surface coverage on reaction barriers and energies is explored as well. The performed calculations suggest that the desired alkane product is formed from a ketone intermediate on Ru, and through both ketone and alcohol on Rh, although the selectivity towars alkane on Rh is much lower than on Ru.

Emulating “Curvature‐Enhanced Adsorbate Coverage” for Superconformal and Orientated Zn Electrodeposition in Zinc‐ion‐Batteries

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature‐enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure orientates the superconformal Zn deposition owing to the spatial deposition rate of the rearranged crystal planes, promoting bottom‐up “superfilling” of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra‐long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12%. The Zn|Na2V6O16·3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high‐performance zinc‐ion batteries.

Emulating "Curvature-Enhanced Adsorbate Coverage" for Superconformal and Orientated Zn Electrodeposition in Zinc-ion-Batteries.

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature-enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure orientates the superconformal Zn deposition owing to the spatial deposition rate of the rearranged crystal planes, promoting bottom-up "superfilling" of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra-long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12%. The Zn|Na2V6O16·3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high-performance zinc-ion batteries.

Application of Reduced Graphene Oxide-Zinc Oxide Nanocomposite in the Removal of Pb(II) and Cd(II) Contaminated Wastewater

Toxic metal wastewater is a challenge for exposed terrestrial and aquatic environments, as well as the recyclability of the water, prompting inputs for the development of promising treatment methods. Consequently, the rGO/ZnONP nanocomposite was synthesized at room temperature for four hours and was tested for the adsorption of cadmium and lead in wastewater. The optimized nanocomposite had the lowest band gap energy (2.69 eV), and functional group interactions were at 516, 1220, 1732, 3009, and 3460 cm−1. The nanocomposite showed good ZnO nanoparticle size distribution and separation on rGO surfaces. The nanocomposite’s D and G band intensities were almost the same, constituting the ZnO presence on rGO from the Raman spectrum. The adsorption equilibrium time for cadmium and lead was reached within 10 and 90 min with efficiencies of ~100%. Sips and Freundlich best fitted the cadmium and lead adsorption data (R2 ~ 1); therefore, the adsorption was a multilayer coverage for lead and a mixture of heterogenous and homogenous coverage for cadmium adsorption. Both adsorptions were best fitted by the pseudo-first-order model, suggesting the multilayer coverage dominance. The adsorbent was reused for three and seven times for cadmium and lead. The nanocomposite showed selectivity towards lead (95%) and cadmium (100%) in the interfering wastewater matrix. Conclusively, the nanocomposite may be embedded within upcoming lab-scale treatment plants, which could lead to further upscaling and it serving as an industrial wastewater treatment material.

Separation of C6 hydrocarbons on sodium dithionite reduced graphene oxide aerogels

The ability of reduced graphene oxide aerogels (rGOAs) for challenging gas-phase separation was investigated with hexane isomers and benzene (C6 hydrocarbons) using inverse gas chromatography (IGC). For the first, rGOAs were synthesized with sodium dithionite (DTN) as a reductant. Experiments revealed that the most optimal DTN to graphene oxide mass ratio was 2:1, resulting in the highest specific surface area of 432.3 m2 g−1 and the highest degree of graphitization among analyzed samples. C6 hydrocarbon adsorption tests demonstrated the dominant role of the kinetic effect for the adsorption of branched and cyclic hexane isomers - the partition coefficient decreased as the molecule kinetic diameter increased. The contribution of thermodynamic effects was distinguished for molecules with uneven charge distribution. A comparison of the partition coefficient ratios for different pairs of hydrocarbons demonstrated the potential of rGOAs in separating various C6 hydrocarbons. The selectivity, calculated from binary-component adsorption tests of benzene (Bz)/cC6 equimolar mixture, was 13.7, 8.5 and 2.8 for DTN4, DTN2, and DTN1. The research indicates that rGOAs may have potential as adsorbents for the selective separation of hydrocarbons, however, the competitive adsorption and performance at high surface coverages of adsorbates have to be accounted for in further research to assess the applicability of rGOAs reliably.

Electrowinning for Room-Temperature Ironmaking: Mapping the Electrochemical Aqueous Iron Interface.

A promising route toward room-temperature ironmaking is electrowinning, where iron ore dissolution is coupled with cation electrodeposition to grow pure iron. However, poor faradaic efficiencies against the hydrogen evolution reaction (HER) is a major bottleneck. To develop a mechanistic picture of this technology, we conduct a first-principles thermodynamic analysis of the Fe110 aqueous electrochemical interface. Constructing a surface Pourbaix diagram, we predict that the iron surface will always drive toward adsorbate coverage. We calculate theoretical overpotentials for terrace and step sites and predict that growth at the step sites are likely to dominate. Investigating the hydrogen surface phases, we model several hydrogen absorption mechanisms, all of which are predicted to be endothermic. Additionally, for HER we identify step sites as being more reactive than on the terrace and with competitive limiting potentials to iron plating. The results presented here further motivate electrolyte design toward HER suppression.

Theoretical insight into the NO* Coverage-Dependent selectivity of Pd and Cu electrocatalysts for nitrate reduction

Nitrate (NO3−) is a concerning contaminant in groundwater that is harmful to human health. Electrocatalytic reduction of NO3− can be achieved with transition metals such as Pd and Cu. In this work, we apply density functional theory (DFT) to discern how the electronic properties of the metal catalyst affect the selectivity of the nitrate reduction mechanism toward either N2 products (e.g., N2 and N2O) or N1 products (e.g., NH3 and NH4+). We find that the greater d-band filling of Cu results in more electron accumulation on the N atom of adsorbed NO*, which drives N–H bond formation favoring the production of HNO* and eventually N1 products (NH3). Conversely, the more delocalized d orbitals of Pd lead to a strong adsorbate–adsorbate coverage effect that lowers key N–N coupling barriers at high NO* coverage favoring selectivity toward N2 products (N2 and N2O). This work elucidates why, at the electronic-structure level, nitrate reduction is highly sensitive to NO* coverage on some metals (such as Pd) and less so on others (such as Cu).

The Impact of Metal Centers in the M-MOF-74 Series on Formic Acid Production.

The confinement effect of porous materials on the thermodynamical equilibrium of the CO2 hydrogenation reaction presents a cost-effective alternative to transition metal catalysts. In metal-organic frameworks, the type of metal center has a greater impact on the enhancement of formic acid production than the scale of confinement resulting from the pore size. The M-MOF-74 series enables a comprehensive study of how different metal centers affect HCOOH production, minimizing the effect of pore size. In this work, molecular simulations were used to analyze the adsorption of HCOOH and the CO2 hydrogenation reaction in M-MOF-74, where M = Ni, Cu, Co, Fe, Mn, Zn. We combine classical simulations and density functional theory calculations to gain insights into the mechanisms that govern the low coverage adsorption of HCOOH in the surrounding of the metal centers of M-MOF-74. The impact of metal centers on the HCOOH yield was assessed by Monte Carlo simulations in the grand-canonical ensemble, using gas-phase compositions of CO2, H2, and HCOOH at chemical equilibrium at 298.15-800 K, 1-60 bar. The performance of M-MOF-74 in HCOOH production follows the same order as the uptake and the heat of HCOOH adsorption: Ni > Co > Fe > Mn > Zn > Cu. Ni-MOF-74 increases the mole fraction of HCOOH by ca. 105 times compared to the gas phase at 298.15 K, 60 bar. Ni-MOF-74 has the potential to be more economically attractive for CO2 conversion than transition metal catalysts, achieving HCOOH production at concentrations comparable to the highest formate levels reported for transition metal catalysts and offering a more valuable molecular form of the product.

(Invited) Adsorbate Coverage Steers Selectivity during Catalytic Nitrate Reduction

Nitrate (NO3 -) is a pervasive contaminant in groundwater that is harmful to human health. In this talk, we will discuss strategies for developing (electro)catalysts that selectively reduce NO3 - to either dinitrogen (N2), which is the desirable product if the goal is to remove NO3 - from drinking water, or to ammonia (NH3), which is the desirable produce for resource recovery. Using density functional theory (DFT), we found that product selectivity to NH3 versus N2 is controlled by competition between N-H bond formation and N-N bond formation on Cu and Pd surfaces. On the Cu(100) surface, N-H bond formation is favorable in the hydrogenation step of surface-bound NO*. This leads to the formation of an HNO* intermediate that is readily reduced to NH3. On the Pd(100) surface, NO* is hydrogenated to form an NOH* intermediate that is readily reduced to N*. N2 then is generated through a N*-NO* coupling step. Importantly, we found that the N-N bond formation barrier on Pd is highly dependent on the NO* surface coverage, where a high NO* coverage lowers the N*-NO* coupling barrier. As such, increased NO* coverage enhances N2 selectivity. Using this concept, we worked with collaborators to design a Pd nanocube electrocatalyst with partial Cu coverage that achieves high NO3 - reduction activity and N2 selectivity by increasing NO* coverage through a Cu-to-Pd spillover mechanism (ACS Catal. 2023, 13, 1, 87–98). This work highlights the importance of NO* surface coverage for controlling product selectivity, explains the different selectivity observed for Cu and Pd, and demonstrates strategies for boosting N2 selectivity through NO* spillover.

Contrasting Metallic (Rh0) and Carbidic (2D-Mo2C MXene) Surfaces in Olefin Hydrogenation Provides Insights on the Origin of the Pairwise Hydrogen Addition.

Kinetic studies are vital for gathering mechanistic insights into heterogeneously catalyzed hydrogenation of unsaturated organic compounds (olefins), where the Horiuti-Polanyi mechanism is ubiquitous on metal catalysts. While this mechanism envisions nonpairwise H2 addition due to the rapid scrambling of surface hydride (H*) species, a pairwise H2 addition is experimentally encountered, rationalized here based on density functional theory (DFT) simulations for the ethene (C2H4) hydrogenation catalyzed by two-dimensional (2D) MXene Mo2C(0001) surface and compared to Rh(111) surface. Results show that ethyl (C2H5*) hydrogenation is the rate-determining step (RDS) on Mo2C(0001), yet C2H5* formation is the RDS on Rh(111), which features a higher reaction rate and contribution from pairwise H2 addition compared to 2D-Mo2C(0001). This qualitatively agrees with the experimental results for propene hydrogenation with parahydrogen over 2D-Mo2C1-x MXene and Rh/TiO2. However, DFT results imply that pairwise selectivity should be negligible owing to the facile H* diffusion on both surfaces, not affected by H* nor C2H4* coverages. DFT results also rule out the Eley-Rideal mechanism appreciably contributing to pairwise addition. The measurable contribution of the pairwise hydrogenation pathway operating concurrently with the dominant nonpairwise one is proposed to be due to the dynamic site blocking at higher adsorbate coverages or another mechanism that would drastically limit the diffusion of H* adatoms.

The role of coordinating anions in the supporting electrolyte during the electrocatalytic oxidation of glycerol on Pt electrodes

This research explores the glycerol electrooxidation reaction (GEOR) on a platinum electrode, with a special emphasis on the role of the chemical properties of the anion present in the electrolyte composition. Essential knowledge of the mechanism and dynamics of glycerol electrooxidation is obtained through comprehensive studies that involve in situ FTIR measurements and the analysis of electrochemically oscillatory responses. This study addresses on the complex interplay between anion adsorption strength and the GEOR, focusing on the differences in CO adsorption coverage, which is the main strongly adsorbed intermediate. The anion adsorption strength, with the order HClO4 < H2SO4 < H3PO4, affects significantly not only the CO coverage on the platinum surface but also the overall glycerol electrooxidation rate. The observed differences in the electroactivity are attributed to competitive adsorption phenomena, in which specific coordinated ions have greater adsorption capabilities than perchlorate ions. These findings highlight the critical relevance of designing and optimizing electrocatalysts for glycerol electrooxidation and related processes with careful consideration of the electrolyte composition, notably the anion.

The Conundrum of "Pair Sites" in Langmuir-Hinshelwood Reaction Kinetics in Heterogeneous Catalysis.

Understanding reaction kinetics is crucial for designing and applying heterogeneous catalytic processes in chemical and energy conversion. Here, we revisit the Langmuir-Hinshelwood (L-H) kinetic model for bimolecular surface reactions, originally formulated for metal catalysts, assuming immobile adsorbates on neighboring pair sites, with the rate varying linearly with the density of surface sites (sites per unit area); r ∝ [*]o 1. Supported metal oxide catalysts, however, offer systematic control over [*]o through variation of the active two-dimensional metal oxide loading in the submonolayer region. Various reactions catalyzed by supported metal oxides are analyzed, such as supported VO x catalysts, including methanol oxidation, oxidative dehydrogenation of propane and ethane, SO2 oxidation to SO3, propene oxidation to acrolein, n-butane oxidation to maleic anhydride, and selective catalytic reduction of nitric oxide with ammonia. The analysis reveals diverse dependencies of reaction rate on [*]o for these surface reactions, with r ∝ [*]o n , where n equals 1 for reactions with a unimolecular rate-determining step and 2 for those with a bimolecular rate-limiting step or exchange of more than 2 electrons. We propose refraining from a priori assumptions about the nature and density of surface sites or adsorbate behavior, advocating instead for data-driven elucidation of kinetics based on the density of surface sites, adsorbate coverage, etc. Additionally, recent studies on catalytic surface mechanisms have shed light on nonadjacent catalytic sites catalyzing surface reactions in contrast to the traditional requirement of adjacent/pair sites. These findings underscore the need for a more nuanced approach in modeling heterogeneous catalysis, especially supported metal oxide catalysts, encouraging reliance on experimental data over idealized assumptions that are often difficult to justify.

Uncovering the Dissociative Adsorption of the Leveler Janus Green B on Cu Electrodes at the Molecular Level.

The interfacial adsorption structure of an organic leveler decides its functionality in Cu interconnect electroplating and is yet far from clear. In this work, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and electrochemical quartz crystal microbalance (EQCM) in conjunction with density functional theory (DFT) calculations are applied to unravel the interfacial adsorption of the classic dye leveler Janus Green B (JGB) at a Cu electrode and understand its polarization property against Cu electrodeposition from an adsorption structure perspective. ATR-SEIRAS measurements and DFT calculations reveal that the N=N bond of the JGB molecule splits via reductive hydrogenation, forming two fragments of contrasting adsorption configurations. JGB exhibits the strongest inhibition effect on Cu deposition among all the tested additives including individual and mixed fragments, due to the highest coverage of organic adsorbates from JGB dissociation, as measured by EQCM. This work highlights the advantage of surface sensitive analytical tools in understanding the structure-performance of levelers.

Electronic properties tailoring of th-XN (X = B, al) by surface functionalization

Hydrogenation and fluorination is a significant method to tune the electronic properties of two-dimensional (2D) materials. This paper theoretically predicted and analyzed the effects and regulatory mechanisms of surface functionalization on the electronic properties of 2D semiconductor tetrahex Boron/Aluminium Nitride (th-BN/th-AlN). The density-functional theory (DFT) calculations were employed to study various trends of band structure, effective mass, and work function. The results show that the electronic properties of 2D th-BN/th-AlN are susceptible to the surface adsorption atom species and coverage. Interconversions between semiconductor and metal properties or indirect and direct band structures in 2D th-XN (X = B, Al) can be realized by hydrogen and fluorine surface adsorption. The band gap expands and the work function decreases after H atom is adsorbed on the surface, while the band gap first increases and then decreases and the work function expands after F is adsorbed on the surface. After functionalization, the effective mass of the hole will be reduced to even lighter than that of an electron in certain directions. The change mechanisms of electronic properties in th-BN/AlN is surface adsorbed atoms will cause sp2-hybridized atoms to turn into sp3-hybridized atoms, which leads to the polarized double bonds between adjacent atoms becoming a single σ bond. The chemical bond changing will result in the band near the Fermi level gradually disappearing.

Impact of aragonite coral powder on hydration, strength, and rheology of cement paste

Understanding the intricate bonding mechanism between coral reef surfaces and C–S–H is crucial for advancing large-scale engineering applications. This study conducts a comprehensive analysis of the impact of coral powder (CP) on cement paste. Initially, zeta potential experiments were performed to probe ion adsorption from the cement pore solution at the CP interface. We propose a novel model to quantify the adsorption of Ca2+ by CP. Subsequently, the study delves into the morphological properties of C–S–H nucleation and growth at this interface and formulates an equation elucidating the CP and Ca2+ adsorption relationship. Then, the crack extension behavior of cementitious materials was scrutinized. Finally, an examination of CP effects on the rheological properties of fresh cement pastes is presented. The findings indicate that CP particles exhibit a notably weaker adsorption affinity with Ca2+ compared to their interaction with SO42−. Compared to limestone (LP), CP exhibited a 32.1 % reduction in Ca2+ adsorption in Ca(OH)2 solutions, 44.2 % reduction in Ca(OH)2 + 10 mmol/L K2SO4, and 40.6 % reduction in Ca(OH)2 + 50 mmol/L K2SO4 solutions. Higher zeta potential values correspond to stronger Ca2+ adsorption and broader surface coverage of Ca2+. The inferior surface characteristics of CP hinder C–S–H nucleation and growth, leading to a low CH orientation index in cement paste containing CP. These pastes exhibit cracks more frequently between CP and hydration products. An attractive force is observed between CP and cement particles, decreasing cement paste flowability.

Potential-dependent insights into the origin of high ammonia yield rate on copper surface via nitrate reduction: A computational and experimental study

Focusing on revealing the origin of high ammonia yield rate on Cu via nitrate reduction (NO3RR), we herein applied constant potential method via grand-canonical density functional theory (GC-DFT) with implicit continuum solvation model to predict the reaction energetics of NO3RR on pure copper surface in alkaline media. The potential-dependent mechanism on the most prevailing Cu (111) and the minor (100) and (110) facets were established, in consideration of NO2−, NO, NH3, NH2OH, N2, and N2O as the main products. The computational results show that the major Cu (111) is the ideal surface to produce ammonia with the highest onset potential at 0.06 V (until −0.37 V) and the highest optimal potential at −0.31 V for ammonia production without kinetic obstacles in activation energies at critical steps. For other minor facets, the secondary Cu (100) shows activity to ammonia from −0.03 to −0.54 V with the ideal potential at −0.50 V, which requires larger overpotential to overcome kinetic activation energy barriers. The least Cu (110) possesses the longest potential range for ammonia yield from −0.27 to −1.12 V due to the higher adsorption coverage of nitrate, but also with higher tendency to generate di-nitrogen species. Experimental evaluations on commercial Cu/C electrocatalyst validated the accuracy of our proposed mechanism. The most influential (111) surface with highest percentage in electrocatalyst determined the trend of ammonia production. In specific, the onset potential of ammonia production at 0.1 V and emergence of yield rate peak at −0.3 V in experiments precisely located in the predicted potentials on Cu (111). Four critical factors for the high ammonia yield and selectivity on Cu surface via NO3RR are summarized, including high NO3RR activity towards ammonia on the dominant Cu (111) facet, more possibilities to produce ammonia along different pathways on each facet, excellent ability for HER inhibition and suitable surface size to suppress di-nitrogen species formation at high nitrate coverage. Overall, our work provides comprehensive potential-dependent insights into the reaction details of NO3RR to ammonia, which can serve as references for the future development of NO3RR electrocatalysts, achieving higher activity and selectivity by maximizing these characteristics of copper-based materials.

An investigation of modified dialdehyde starch as a highly efficient green corrosion inhibitor for carbon steel in 1 M HCl medium: Synthesis, experimental and theoretical studies

Compared to small organic molecule corrosion inhibitors, polymer corrosion inhibitors offer numerous advantages in terms of adsorption coverage on the metal surface and the presence of multiple active sites for adsorption. A dialdehyde starch Schiff base was synthesized by modification of natural polymer starch and tetraethylene pentaamine, and it was characterized by X-ray diffraction, gel chromatography and thermogravimetry. The corrosion inhibition behaviors of dialdehyde starch Schiff base as an oligomer for low carbon steel in 1 M HCl were investigated. Compared to the common starch derivatives, the dialdehyde starch Schiff base has good water solubility and inhibition performance. The inhibition efficiency can reach 93.2% with 0.16 mM in 1 M HCl solution at 333 K. Double aldehyde starch Schiff base is a mixed corrosion inhibitor that mainly inhibits cathodic reactions. Its adsorption on the surface of carbon steel follows the Langmuir adsorption equation, and the nitrogen -containing groups in the molecules are adsorbed on the surface of the steel through physical and chemical reactions. Quantum chemical calculations confirmed the experimental results.